I. Field
The present disclosure relates generally to communication, and more specifically to techniques for searching for wireless communication systems.
II. Background
Wireless communication systems are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless systems may be multiple-access systems capable of supporting multiple users by sharing the available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, and Single-Carrier FDMA (SC-FDMA) systems.
A wireless device (e.g., a cellular phone) may be able to receive service from one or more wireless systems. Upon power up, the wireless device may search for a wireless system from which it may receive service. If a system is found, then the wireless device may register with the system. The wireless device may then actively communicate with the system or go into an idle mode if communication is not required. If the wireless device subsequently loses the system, then it may enter an out-of-service (OOS) state and attempt to acquire a system from which service may be obtained.
The wireless device may not have any knowledge of its operating environment while in the OOS state and may not know which systems, if any, can be acquired. The wireless device may also have no knowledge on when it may be able to acquire a system since this may depend on various factors such as user mobility. The wireless device may consume a large amount of battery power if it continuously searches for systems while in the OOS state. This heavy battery power consumption may significantly reduce both standby time and talk time, especially when the OOS duration is long. The wireless device may search for systems infrequently in order to conserve battery power. However, the infrequent search may significantly delay system acquisition.
There is therefore a need in the art for techniques to efficiently search for wireless systems in the OOS state.